Pressure the Gas Laws NAT 45 Physics Pressure
- Slides: 11
Pressure & the Gas Laws NAT 4/5 Physics
Pressure �Pressure is defined as being the Force that acts on a specific Area…… �So before we look at pressure we should really define what force we mean by and how we measure it. �We should also remind ourselves how to measure area and the units it can be measured in.
Force �A force is a push or a pull. �Force ‘F’ is measured in newtons (N) �Force can be measured with a spring balance or a newton balance. �Bathroom scales measure the force that gravity pulls you down with. Some bathroom scales can measure in newtons.
Mass and weight…. . �In physics it is very important to know the difference between mass and weight…. �Mass ‘m’ is the amount of ‘stuff’ in an object. It is measured in kilograms (kg) for example a 1 kg bag of sugar contains 1 kg of the substance – sugar Mass does not change as long as you don’t add or take away any of the ‘stuff’ in it.
Weight �Weight ‘W’ is a measure of the force that gravity pulls you down with. �Since weight is a force downwards, it should be measured in newtons (N) �Weight depends on the size of Gravity! �On Earth gravity: ‘g’ = 9. 8 Nkg-1 �This means there is a force of 9. 8 newtons pulling down on every kg of mass.
Weight & Mass �To calculate the weight of an object in newtons (N) you simply multiply its mass by the value for gravity.
Pressure is defined as the force that acts on a specific area Force is measured in newtons (N) Area is measured in square metres (m 2) Pressure is measured in pascals (Pa) (1 Pa = 1 Nm-2) (there are 10, 000 cm 2 in 1 m 2)
Pressure example: �An elephant has a mass of 700 kg. The area of one of its feet is 0. 07 m 2. �What is the weight of the elephant? �What is the pressure it exerts on the floor when standing on �a) 4 feet �b) 1 foot
Man on thin ice - discuss
Pressure and area The smaller the area , the greater the pressure
Air Pressure Air particles are moving about randomly in all directions. When they hit the walls of the container they are in , they produce a Force on the surface Area of the container All these tiny forces add up to produce a Pressure on all surfaces of the container. This is called air pressure. Air Pressure on Earth at sea level is: 100, 000 Pa watch This means there is a force of 100, 000 N acting on every square metre!!
